.back-btn {
    position: fixed;
    bottom: 20px;
    left: 50%;
    transform: translateX(-50%);
    padding: 10px 20px;
    background: #fff;
    border-radius: 20px;
    text-decoration: none;
    color: #ff6b6b;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}
.spark {
    width: 10px;
    height: 10px;
    background: #fff;
    position: absolute;
    border-radius: 50%;
    animation: sparkle 1s ease-out;
}

@keyframes sparkle {
    from {
        transform: scale(1);
        opacity: 1;
    }
    to {
        transform: scale(3);
        opacity: 0;
    }
}